This summer is critical for butterflies as common species have fallen into decline, Sir David Attenborough has warned.
The dry spring and early summer experienced this year could be a breath of fresh air for species such as the Small Tortoiseshell, Peacock, Meadow Brown and Gatekeeper.
Worryingly, the native butterflies which were once common fell in number last year, which was the fourth worst year on record for the winged insects.
Legendary naturalist Sir David was urging members of the public to venture out into parks and gardens to help keep accurate records of the butterfly population.
Known as the Big Butterfly Count, the three weeks between July 14 and August 6 will be a chance for aspiring Attenboroughs to go out and spend 15 minutes in the sunshine.
It involved keeping a log of 18 common species of butterfly, and two species of moths, and is the largest survey of it's kind around the world.
Sir David said: "The next few weeks are a vital period for our butterflies.
"They need to make the most of this chance to feed and breed. So far the warm weather has given some species like the Meadow Brown, Red Admiral and Ringlet a good start but butterflies really need this to continue.
"Last year, despite a warm summer, butterflies like the Small Tortoiseshell, Peacock, Meadow Brown and Gatekeeper saw their numbers fall as a warm winter and cold spring earlier in the year led to problems that affected their numbers later on.
"Worryingly, we are now seeing the fortunes of some of our once common butterflies mirror those of our rarest species.
"They too are now also suffering significant declines with butterflies declining more rapidly in urban areas than in the countryside.
"In the last decade our butterflies have experienced several poor years and although resilient, they simply cannot sustain repeated losses, especially if the habitats they need in order to rebuild their populations are also under threat."
More than three-quarters of the UK's butterflies have declined in the last 40 years with some common species, such as the Small Tortoiseshell, suffering significant slumps.
Cities and towns are experiencing a more rapid decline in numbers, new data showed.
Butterflies play a crucial role in the production of food, as much like bees, they act as pollinators.
Sir David, president of Butterfly Conservation, added: "Taking part in the Big Butterfly Count is good for butterflies and it is also good for us all.
"The Count is good for butterflies because your sightings will tell us which species need help and in which areas we need to help them.
"But the Big Butterfly Count is also good for you because 15 minutes spent watching butterflies in the summer sunshine is priceless.
"Spending time with butterflies lifts the spirits and reinvigorates that sense of wonder in the natural world."
Results can be recorded or online or on an app, and the event will be launched at the London Wetland Centre.
The count is entering it's seventh year, and the research will help guide how to identify trends which will help protect butterflies from extinction.
Richard Fox, Butterfly Conservation Head of Recording said: "With increasing numbers of our common and widespread butterflies in long-term decline, Big Butterfly Count is more important than ever.
"Simply taking 15 minutes out of your normal day to enjoy the sunshine and count butterflies can help us monitor their populations. It's a win-win for wildlife."